FIG. 12 is an exploded perspective view of a speaker used as a “receiver” for a conventional portable telephone. For a conventional speaker, a diaphragm, vibration system, and magnetic circuit are shaped substantially circular, as shown in FIG. 12.
The speaker shown in FIG. 12 comprises cylindrical yoke 1 having magnet 2 attached to a bottom thereof, top plate 3 bonded on the magnet 2, diaphragm 6 having voice coil 6a attached thereto, protector 10, damping cloth 10a covering sound holes of the protector 10, and resin case 7. The protector 10 and the damping cloth 10a protect the diaphragm 6 from a force applied from outside and restrict excessive amplitudes of the diaphragm 6 at resonance.
An inner wall of the cylindrical yoke 1 and the top plate 3 form a ring-shape magnetic gap (not shown). The yoke 1, the magnet 2, and the top plate 3 form a magnetic circuit 4. The magnetic circuit 4 is integrated into the case 7 by an insert molding, a fitting, a bonding, or other method. The case 7 further has insert-molded external connection terminals 8 and internal connection terminals (not shown) connected to the external connection terminals. To the internal connection terminals, leads drawn out from the voice coil 6a are connected.
The outer periphery of the diaphragm 6 is bonded to case 7 by adhesive material, with the voice coil 6a inserted into the magnetic gap in the magnetic circuit 4.
In the speaker structured as above, sound signals are fed into the voice coil 6a via the external connection terminals 8 and the internal connection terminals and drive the voice coil 6a vertically and vibrate the diaphragm 6, thereby producing sound. According to one of the mounting methods of the speaker, each terminal 8 is formed of a spring material or the like and spring pressure produced by bent portion 8a of the spring material brings terminal 8 into contact with the power supply section of the equipment, as shown in FIG. 13.
In recent years, with a demand of a more multi-functional portable telephone, a larger display has been designed, and thus a saving in receiver space, i.e. a much smaller-sized speaker has been required. However, for a production of the smaller-sized speaker, a more precise assembling technique is required and stabilizing its quality is difficult. In addition, the smaller area of the diaphragm poses a problem of deterioration of sound quality and decrease in sound pressure of the speaker.
For an installation in a smaller space, a rectangular speaker is more effective than a circular speaker. However, a conventional rectangular speaker for use in a television set or the like, as described in the Japanese Patent Laid-Open Publication No. H10-94090, for example, cannot be downsized, using the same structure and materials.
The major reason is the dimension of the speaker. A receiver for use in a portable telephone measures, for example, 1.5 cm in length, 0.6 cm in width, and 0.25 cm in thickness. For these dimensions, conventional flexible wires for connecting the internal connection terminals and the voice coil cannot be used. In other words, the flexible wires must have a specific diameter large enough to cope with the amplitudes of the diaphragm. It is difficult to produce a flexible wire suitable for the dimensions required for the portable telephones or other portable electronic equipment. Also in a conventional circular speaker, wires for connecting the internal connection terminals and the voice coil are so short that excessive force applied thereto may break the wires.
Furthermore, in a case where the terminal 8 is brought into contact with the power supply section using spring pressure, excess bending of the bent portion 8a of the spring exceeds the reversible threshold of the spring of the terminal 8, when a value of the dimension at which the speaker is inserted into the equipment is set to a large value. In this case, the decreased spring pressure of terminal 8 results in unstable contact between the terminal and the power supply section. This unstable contact has a problem in that shocks or vibrations applied to the equipment may cause a contact failure and interrupt signals.
The present invention provides a small and rectangular speaker suitable for a portable electronic equipment that addresses the problems described above.